Magnetic disk device

ABSTRACT

According to one embodiment, a magnetic disk device includes a disk including a first region and a second region different from the first region, a head that writes data on the disk and reads data from the disk, an actuator that positions the head on the disk, and a controller which positions the head by driving the actuator and writes data in the first region and the second region with the head, a skew angle of the head with respect to a circumferential direction of the disk varying within a first angle in the first region, and varying, in the second region, from a second angle larger than the first angle to a third angle larger than the first angle and the second angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-055356, filed Mar. 22, 2018, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic disk device.

BACKGROUND

The magnetic disk device, includes an actuator for positioning the headattached to the tip at a target position on the disk. In the magneticdisk device, the skew angle of the head with respect to thecircumferential direction of the disk usually changes within aparticular angle range. In order to improve the random accessperformance, a magnetic disk device having an actuator shorter(hereinafter referred to as a short actuator) than a normal actuator isstudied. The range of the skew angle of the head by the short actuatoris larger than the range of the skew angle of the head by the normalactuator. Therefore, in a magnetic disk device provided with a shortactuator, a recording region of a disk is divided into a where therecording quality of data can be ensured and a region where therecording quality of data can not be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of the configuration ofa magnetic disk device according to a first embodiment;

FIG. 2 is a plan view schematically showing an example of a disk;

FIG. 3 is a diagram showing an example of the relation between theradial position and the skew angle of the disk;

FIG. 4 is a diagram showing an example of a magnetization patternwritten on the disk with each skew angle;

FIG. 5 as a diagram showing an example or a magnetization patternwritten on the disk with each skew angle;

FIG. 6 is a diagram showing an example of tracks in each region of thedisk;

FIG. 7 is a diagram showing an example of part of tracks arranged in aspiral shape in a second data region;

FIG. 8 is a diagram showing an example of tracks arranged in a spiralshape at a track angle in the second data region;

FIG. 9 is a diagram showing an example of tracks arranged in a spiralshape at a track angle in the second data region;

FIG. 10 is a diagram showing an example of the relation between theradial position and the angle of the head with respect to the trackdirection in a case where the track is written in a spiral shape at atrack angle in the second data region;

FIG. 11 is a diagram showing an example of part of: tracks arranged at atrack angle that changes according to the skew angle in the second dataregion;

FIG. 12 is a view showing an example of tracks arranged in a spiralshape at a track angle which changes according to the skew angle in thesecond data region;

FIG. 13 is a diagram showing an example of tracks arranged in a spiralshape at a track angle θtd changing according to the skew angle in thesecond data region;

FIG. 14 is a view showing an example of a track angle that changesaccording to the skew angle;

FIG. 15 is a diagram showing an example of the relation between theradial position and the difference angle with respect to a trackdirection in a case where a track is written in a spiral shape at atrack angle that changes according to a skew angle in the second dataregion;

FIG. 16 is a diagram showing an example of an LBA according to the firstembodiment;

FIG. 17 is a diagram showing an example of command processing accordingto the first embodiment;

FIG. 18 is a flowchart showing an example of a track angle determinationmethod according to the first embodiment;

FIG. 19 is a block diagram showing an example of the positioning controlsystem of the magnetic disk device;

FIG. 20 is a flowchart showing an example of a head positioning controlmethod in the second data region according to a first modification;

FIG. 21 is a cross-sectional view schematically showing an example of aconfiguration of a disk according to a second modification;

FIG. 22 is a view showing an example of a change in the thickness of thedisk according to the second modification;

FIG. 23 is a schematic diagram showing an example of a configuration ofa magnetic disk device according to a second embodiment;

FIG. 24 a diagram showing an example of an LBA according to the secondembodiment;

FIG. 25 is a diagram showing an example of command processing accordingto the second embodiment;

FIG. 26 is a diagram showing an example of command processing accordingto the second embodiment; and

FIG. 27 is a flowchart showing an example of command processingaccording to the second embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a magnetic disk devicecomprises: a disk including a first region and a second region differentfrom the first region; a head that writes data on the disk and readsdata from the disk; an actuator that positions the head on the disk; anda controller which positions the head by driving the actuator and writesdata in the first region and the second region with the head, a skewangle of the head with respect to a circumferential direction of thedisk varying within a first angle in the first region, and varying, inthe second region, from a second angle larger than the first angle to athird angle larger than the first angle and the second angle.

According to another embodiment, a magnetic disk device comprises: adisk including a first region and a second region different from thefirst region; a head that writes data on the disk and reads data fromthe disk; and a controller which positions the head by driving theactuator and writes data in the first region and the second region withthe head, a thickness of the second region being greater than that ofthe first region.

According to another embodiment, a magnetic disk device comprises: adisk including a first region and a second region different from thefirst region; a head that writes data on the disk and reads data fromthe disk; and a controller which preferentially processes a firstcommand for executing a read/write processing on a first region of thedisk over a second command for executing a read/write processing on asecond region of the disk.

Hereinafter, embodiments will be desorbed with reference to thedrawings. It should be noted that the drawings are merely examples anddo not limit the scope of the invention.

First Embodiment

FIG. 1 is a schematic diagram showing an example of a configuration of amagnetic disk device 1 according to the first embodiment.

The magnetic disk device 1 includes a housing HS, a head disk assembly(HDA) 10, a driver 1020, a head amplifier integrated circuit(hereinafter referred to as a head amplifier IC or a preamplifier) 30, avolatile memory 70, a buffer memory (Buffer) 80, a nonvolatile memory90, and a system controller 130 which is an integrated circuit of onechip. Further, the magnetic disk device 1 is connected to a host system(hereinafter simply referred to as a host) 100. FIG. 1 shows a crosssection of the HDA 10.

The HDA 10 includes a magnetic disk (hereinafter referred to as a disk)DK, a spindle motor (hereinafter referred to as an SPM) 13 that rotatesthe disk DR around a spindle 12, an arm AM on which the head HD ismounted, a voice coil motor (hereinafter referred to as a VCM) 14. TheSPM 13 and the VCM 14 are fixed to the housing HS. The disk DK isattached to the spindle 12 and rotates by driving the SPM 13. The headHD faces the disk DR. The arm AM and the VCM 14 constitute an actuatorAC. The actuator AC rotates about the rotation axis to position the headHD attached to the tip of the arm AM at a particular position of thedisk DK. The arm 13 of the actuator AC according to the presentembodiment is configured to he shorter than, for example, an arm of anormal actuator. Hereinafter, the actuator AC according to the presentembodiment may be referred to as a short actuator AC in some cases. Byshortening the arm AM compared with the arm of the normal actuator inthis way, the inertia of the actuator AC is reduced, and the head HD canbe moved at a high speed. At least two disks DK and at least two headsHD may be provided.

FIG. 2 is a plan view schematically showing an example of thearrangement of the head HD with respect to the disk DK. The firstdirection X, the second direction F, and the third direction Z in thefigure are orthogonal to each other. They may intersect in a state otherthan orthogonal state. The direction toward the tip of the arrowindicating the third direction Z is referred to as upward (or simply up)and the direction opposite from the tip of the arrow indicating thethird direction Z is referred to as downward (or simply down).Hereinafter, a direction orthogonal to the radial direction of the diskDK is referred to as a circumferential direction. In the radialdirection, the direction toward the spindle 12 is referred to as inward(or the inward direction), and the direction opposite to inward (or theinward direction) is referred to as outward (the outward direction).FIG. 2 shows the rotation direction of the disk DK in thecircumferential direction. It should be rioted that the rotationdirection may be opposite. In addition, FIG. 2 shows an angle(hereinafter referred to as a skew angle, a yaw angle, or an azimuthangle) θs with respect to the circumferential direction (or rotationdirection) of the head HD. The skew angle θs toward the inward directionis positive and the angle toward the outward direction is negative. Theskew angle θs may be negative when the angle is toward the inwarddirection and may be positive when the angle is toward the outwarddirection.

In the disk DK, a user data region UA that can be used by a user in aregion in which the data can be written, and a system area SA forwriting information necessary for system management (hereinafterreferred to as system information) are allocated. In the example shownin FIG. 2, a user data region UA is the region from the radial positionIMP (hereinafter referred to as the radial position) of the disk DK tothe radial position OBP. The radial position IMP corresponds to theradial position of the innermost periphery of the disk DK. The systemarea SA is a region from the radial position OMP to the radial positionOBP. The radial position OMP corresponds to the radial position of theoutermost periphery of the disk DK. The system area SA may not beallocated. The user data region UA is divided into a first data regionUA1 and a second data region UA2. The first data region UA1 is a regionfrom the radial position OBP to the radial position ISP. The radialposition OBP corresponds to the boundary between the system area SA andthe first data region UA1. Data which is available to the user and isaccessed with high frequency (hereinafter referred to as high accessdata) is written in the first data region UA1. The high access data isequivalent to, for example, hot data. The high access data includes, forexample, user data (hereinafter also referred to as first user data) andthe like. Here, “access” is used as a term including the meaning of“writing data on disk DK” and. “reading data from disk DK”. In addition,“access frequency” indicates the number of times of access (read/write)within a particular time, that is, the expression of high accessfrequency or low access frequency. The second data region UA2 is aregion from the radial position IBP to the radial position IMP. Theradial position IBP corresponds to the boundary between the first dataregion UA1 and the second data region UA2. In the second data regionUA2, which is available to the user, data having a lower priority or alower access frequency (hereinafter referred to as low access data) thanthe high access data is written. The low access data is equivalent to,for example, cold data and/or warm data. The low access data includesuser data having lower priority or lower access frequency than the firstuser data (hereinafter also referred to as second user data), systeminformation, media cache (MC) data, and the like.

The head HD with the slider as a main body includes a write head WH anda read head RH mounted on the slider so as to face the disk DK. Thewrite head WH writes data on the disk DK. The read head RH reads thedata recorded on the data track on the disk DK. The head HD ispositioned, for example, at a particular radial position (hereinafterreferred to as a radial position) on the disk DK by the short actuatorAC rotating around a bearing BR. In the example shown in FIG. 2, when awrite process or a read process is performed in the user data region UAby the short actuator AC, the head HD is positioned at a particularradial position within the region from the radial position OBP to theradial position IMP. As shown in FIG. 2, when positioned at a particularradial position of the disk DK, the head HD is inclined at a particularskew angle θs with respect to the circumferential direction (rotationdirection). In the example shown in FIG. 2, when the head HD ispositioned at the radial position P0 by the short actuator AC, the skewangle θs of the head HD is 0°. When the head HD is positioned at theradial position IP0 inward relative to the radial position P0 by theshort actuator AC, the skew angle θs of the head HD is positive. Whenthe head HD is positioned at the radial position OP0 outward relative tothe radial position P0 by the short actuator AC, the skew angle θs ofthe head HD becomes is negative.

FIG. 3 is a diagram showing an example of the relation between theradial position of the disk DK and the skew angle θs. In FIG. 3, thevertical axis represents the skew angle and the horizontal axisrepresents the radial position. In FIG. 3, the line L31 indicates achange in the skew angle θs) with respect to the radial position of thedisk DK corresponding to the short actuator AC (hereinafter referred toas a change in the skew angle θs of the short actuator AC. The line L32indicates a change in the skew angle θs (hereinafter referred to as achange an the skew angle θs of a normal actuator) with respect to theradial position of the disk DK corresponding to a normal actuator havingan arm longer than the arm AM of the short actuator AC (hereinafterreferred to simply as the normal actuator).

In the example shown in FIG. 3, when the head HD is moved from theradial position OBP to the radial position IMP by the short actuator ACas indicated by the change L31 in the skew angle θs of the shortactuator AC, the skew angle θs of the head HD changes from the firstboundary angle θba 1 corresponding to the radial position OBP to thethird boundary angle θba 3 corresponding to the radial position IMP. Forexample, the absolute value of the first boundary angle θba 1 and theabsolute value of the second boundary angle θba 2 are the same. Forexample, the first boundary angle θba 1 is −15° and the second boundaryangle θba 2 is 15°. Also, the third boundary angle θba 3 is larger thanthe second boundary angle θba 2. That is, the third boundary angle θba 3is larger than the absolute value of the first boundary angle θba 1. Forexample, the third boundary angle θba 3 is 30°.

In the example shown in FIG. 3, when the head HD is moved from theradial position OBP to the radial position IMP by a normal actuator asindicated by the change L32 in the skew angle θs of the normal actuator,the skew angle θs of the head HD changes from the first boundary angleθba 1 corresponding to the radial position OBP to the second boundaryangle θba 2 corresponding to the radial position IMP.

The driver IC20 controls the driving of die SPM 13 and the VCM 14according to the control of the system controller 130 (morespecifically, an MPU 50 described later). The driver IC20 includes anSPM controller 21 and a VCM controller 22. The SPM controller 21controls the rotation of the SPM 13. The VCM controller 22 controls thedriving of the VCM 14 by adjusting the current to be supplied. Note thatpart of the configuration of the driver IC20 (for example, the SPMcontroller 21 and the VCM controller 22) may be provided in the systemcontroller 130.

The head amplifier IC (preamplifier) 30 amplifies the read signal readfrom the disk DK and outputs it to the system controller 130 (morespecifically, a read/write (R/W) channel 40 to be described later).Further, the head amplifier IC 30 outputs write current corresponding toa signal output from an R/W channel 40 to the head HD. The headamplifier IC 30 includes a write signal controller 31 and a read signaldetection unit 32. The write signal controller 31 adjusts the writecurrent output to the head HD under the control of the system controller130 (more specifically, the MPU 50 described later). The read signaldetection unit 32 detects a signal to be written by a write head and asignal read by a read head. Note that part of the configuration of thehead amplifier IC 30 (for example, the write signal controller 31 andthe read signal detection unit 32) may be provided in the systemcontroller 130.

The volatile memory 70 is a semiconductor memory from which stored datais lost when power supply is cut off. The volatile memory 70 stores dataand the like necessary for processing in each part of the magnetic diskdevice 1. The volatile memory 70 is, for example, a DRAM (Dynamic RandomAccess Memory) or an SDRAM (Synchronous Dynamic Random Access Memory).

The buffer memory 80 is a semiconductor memory that temporarily recordsdata and the like transmitted and received between the magnetic diskdevice 1 and a host 100. It is to be noted that the buffer memory 80 maybe formed integrally with the volatile memory 70. The buffer memory 80is, for example, a DRAM, an SRAM (Static Random Access Memory), anSDRAM, an FeRAM (Ferroelectric Random Access Memory), an MRAM(Magnetoresistive Random Access Memory), or the like.

The nonvolatile memory 90 is a semiconductor memory that records datastored even when power supply is cut off. The nonvolatile memory 90 is,for example, a NOR type or NAND type flash ROM (Flash Read Only Memory(FROM)).

The system controller (controller) 130 is implemented by using a largescale integrated circuit (LSI) referred to as the System-on-a-Chip (SoC)in which a plurality of elements are integrated on a single chip, forexample. The system controller 130 includes the read/write (R/W) channel40, a microprocessor (MPU) 50, and a hard disk controller (HDC) 60. Thesystem controller 130 is electrically connected to the driver IC20, thehead amplifier IC 30, the volatile memory 70, the buffer memory 80, thenonvolatile memory 90, and the host system 100. It should be noted thatthe system controller 130 may include the SPM controller 21, the VCMcontroller 22, the write signal controller 31, and the read signaldetection unit 32. Further, the system controller 130 may include thedriver IC20 and the head amplifier IC 30.

The R/W channel 40 executes signal processing of read data transferredfrom the disk DK to the host 100 and write data transferred from thehost 100 in response to an instruction from the MPU 50 to be describedlater. The R/W channel 40 has a circuit or a function for measuring asignal quality of read data. The R/W channel. 40 is electricallyconnected to the head amplifier IC 30, the MPU50, an HDC 60, and thelike, for example.

The MPU 50 is a main controller that controls each part of the magneticdisk device 1 in response to an instruction from the host 100 or thelike. The MPU 50 controls the actuator AC via the driver IC20 andexecutes servo control for positioning the head HD. The MPU 50 controlsa write operation of the data to the disk DK and selects the savedestination of the write data. In addition, the MPU 50 controls a readoperation of the data from the disk DK and controls the processing ofthe read data. The MPU 50 is connected to each part of the magnetic diskdevice 1. The MPU 50 is electrically connected to the driver IC20, theR/W channel 40, the HDC 60, and the like, for example.

The MPU 50 divides the disk DK into the first data region UA1 in whichthe skew angle θs of the head HD changes from the first boundary angleθba 1 to the second boundary angle θba 2 by driving of the actuator AC,and the second region UA2 in which the skew angle changes from thesecond boundary angle θba 2 to the third boundary angle θba 3 by drivingthe actuator AC.

When the absolute value of the first boundary angle θba 1 is equal tothe absolute value of the second boundary angle θba 2, the MPU 50divides the disk DK into the first data region UA1 in which the skewangle θs of the head HD of the disk DK changes within an absolute valueof the first boundary angle θba 1 by driving the actuator AC, and thesecond region UA2 in which the skew angle changes from the absolutevalue of the first boundary angle θba 1 to the third boundary angle θba3 due to the driving of the actuator AC.

The MPU 50 writes the user data, the media cache data, the systeminformation, and the like in the second data region UA2. For example, inorder to maintain high random access performance, the MPU 50 performscontrol so that the head HD moves between the first data region UA1 andthe second data region UA2 less frequently.

When writing user data in the second data region UA2, the MPU 50 writesthe high access data (hot data) having a high access frequency in thefirst data region UA1 and writes the low access data (cold data and/orwarm data) with a low access frequency in the second data region UA2.The MPU 50, for example, at a timing when the queue of a command queueprocessor 632 to be described later is vacant and there is a margin foraccessing the disk DK, moves data (cold data and/or warm data) with alow access frequency in the first data region UA1 to the second dataregion UA2.

When using the second data region UA2 as a media cache, the MPU 50writes the data primarily and sequentially in the first data region UA1after accessing the second data region UA2. Therefore, the head HD movesback and forth between the first data region UA1 and the second dataregion UA2 with a low access frequency, so that the status indicatingthe completion of writing the user data can be returned to the host 100at an earlier timing. For example, the MPU 50 writes data (cached)written in the second data region UA2 to the first data region UA1 at atiming when the queue of the command queue processor 632 to be describedlater is vacant and there is a margin for accessing the disk DK.

When using the second data region UA2 as the system area, the MPU 50writes the system information in the special area in the manufacturingprocess. For example, when starting the magnetic disk device 1, the MPU50 accesses the system area of the second data region UA2 to read thesystem information. In this case, since the timing of accessing thesecond data region UA2 is only the timing such as when the magnetic diskdevice 1 is activated or initialized (re-zero), the head HD moves backand forth between the first data region UA1 and the second data regionUA2 with a low access frequency, so that it is possible to write manysystem information on the disk DK.

In accordance with an instruction from the MPU 50, the HDC 60 controlsread/write processing, and controls data transfer between the, host 100and the R/W channel 40. The HDC 60 is electrically connected to, forexample, the R/W channel 40, the MPU 50, the volatile memory 70, thebuffer memory 80, the nonvolatile memory 90, and the like.

The HDC 60 includes a servo controller 61, a user data controller 62,and a command processor 63. The HDC 60 executes the processes of theseunits, for example, the servo controller 61, the user data controller62, the command processor 63 and the like on the firmware. It should benoted that the HDC 60 may include these units as circuits. Part of theconfiguration of the HDC 60 may be provided in the MPU 50. For example,the servo controller 61, the user data controller 62, and the commandprocessor 63 may be provided in the MPU 50. Further, the HDC 60 mayinclude the configuration and functions of the MPU 50.

The servo controller 61 controls the positioning of the head HD to aparticular position on the disk DK. The servo controller 61 includes atracking controller 611 and a seek controller 612.

The tracking controller 611 controls the head HD so as to follow aparticular position of the disk DK, for example, a particular trackthrough the read/write processing.

The seek controller 612 controls movement (seek) of the head HD on thedisk DK.

The user data controller 62 controls the arrangement of data on the diskDK. Hereinafter, “arranging data (track)” may be used in the samemeaning as “writing data (track)”. For example, the user data controller62 controls the head HD via the servo controller 61, and controls thearrangement of data according to the radial position. The user datacontroller 62 includes, for example, a BPI (Bit Per Inch) control unit621 and a TPI (Tracks Per Inch) control unit 622. A BPI controller 621controls the BPI (linear recording density) according to the radialposition of the disk DK. A TPI controller 622 controls the TPI (trackdensity) according to the radial direction region of the disk DK, forexample, the zone.

FIGS. 4 and 5 are diagrams showing an example of a magnetization patternwritten on the disk DK at each skew angle θs.

The user data controller 62 positions the head HD at a particular radialposition of the disk DK and writes the data on the disk DK with aparticular BPI by the write head WH. In the example shown in FIG. 4, theuser data controller 62 positions the head HD at the radial position P0at which the skew angle θs is zero, and writes data (or track) havingthe data pattern PT1 on the disk DK by the write head WH based on thehigh frequency (HF) write signal. In the data pattern PT1, amagnetization pattern substantially perpendicular to the circumferentialdirection (rotation direction) is repeated. The user data controller 62positions the head HD at the radial position IBP at which the skew angleθs becomes the second boundary angle θba 2, and writes data having thedata pattern PT2 on the disk DK by the write head WH based on the highfrequency (HF) write signal. In the data pattern PT2, a magnetizationpattern inclined according to the write head WH with respect to thecircumferential direction is repeated. The user data controller 62positions the head HD at the radial position IMP at which the skew angleθs becomes the third boundary angle θba 3, and writes data having thedata pattern PT3 on the disk DK by the write head WH based on the highfrequency (HF) write signal. In the data pattern PT3, a magnetizationpattern inclined according to the write head WH with respect to thecircumferential direction is repeated. When the skew angle θs is thethird boundary angle θba 3, since the bevel angle of the rear endportion of the write head WH in the rotation direction is positionedwithin the data width with respect to the circumferential direction, thedata pattern PT3 has a disturbed magnetization pattern in the radiallyinward direction.

In the example shown in FIG. 5, the user data controller 62 positionsthe head HD at the radial position IMP at which the skew angle θsbecomes the third boundary angle θba 3, and writes data having the datapattern PT4 on the disk DK by the write head WH based on the lowfrequency (LF) write signal. In the data pattern PT4, a magnetizationpattern inclined according to the write head WH with respect to thecircumferential direction is repeated. Also in this case, themagnetization pattern of the data pattern PT4 is disturbed in theradially inward direction. In addition, the width of the magnetizationpattern of the data pattern PT4 in the circumferential direction islarger than that of the data pattern PT3.

For example, when reading the data patterns PT3 and PT4 in which themagnetization patterns are disturbed as shown in FIGS. 4 and 5, thesignal quality of the read data, for example, SNR (Signal to noiseratio) deteriorates, compared with the case of reading the data patternsPT1 and PT2. The phenomenon in which the signal quality of datadeteriorates when reading data written by the head HD with the skewangle θs larger than the particular angle is also referred to as azimuthloss. From the examples shown in FIGS. 4 and 5, when data is written bythe head. HD with the skew angle θs larger than the second boundaryangle θba 2, the magnetization pattern of the data pattern is disturbed,and azimuth loss may occur. In other words, when the head HD is inclinedat an angle larger than the second boundary angle θba 2 with respect tothe direction in which the track extends (hereinafter simply referred toas the track direction), the magnetization pattern of the data patternis disturbed, and azimuth loss may occur. That is, when the head HD isinclined at or below the absolute value of the boundary angle θba 2 withrespect to the track direction, the magnetization pattern of the datapattern is not disturbed, so that azimuth loss does not occur.Therefore, when reading the data pattern written by the head HD inclinedat or below the absolute value of the second boundary angle θba 2, thesignal quality of the read data can be ensured. Hereinafter, the secondboundary angle θba 2 may be referred to as an angle θth that ensures thesignal quality of the read/write processing. Further, when the head HDis inclined at an angle larger than the second boundary angle θba 2 withrespect to the track direction, the user data controller 62 can alsoimprove the signal quality by lowering the BPI (linear recordingdensity). In other words, the user data controller 62 can lower the BPI(linear recording density) in the second data region UA2 further thanthat in the first data region UA1. Further, in order to suppressdeterioration of signal quality due to interference by radially adjacenttracks (hereinafter simply referred to as adjacent tracks), the userdata controller 62 can lower TPI (track density), thereby improving thesignal quality. In other words, the user data controller 62 can lowerTPI (track density) in the second data region UA2 further than that inthe first data region UA1.

The user data controller 62 controls the direction (track direction) inwhich data is arranged. For example, when writing data within the rangefrom the first boundary angle θba 1 to the second boundary angle θba 2with respect to the skew angle θs, that is, when writing data to thefirst data region UA1, the user data controller 62 arranges the data(track) in a circular shape. When writing data within the range from thesecond boundary angle θba 2 to the third boundary angle θba 3 withrespect to the skew angle θs, that is, when writing data to the seconddata region UA2, the user data controller 62 arranges the data (track)in a spiral shape.

FIG. 6 is a diagram showing an example of tracks an each region of thedisk DK. FIG. 6 shows a plurality of servo regions SV. Hereinafter, theservo region SV may be referred to as a servo sector in some cases. Theplurality of servo regions SV radially extends in the radial directionof the disk DK and are discretely arranged with a particular interval inthe circumferential direction. In FIG. 6, the servo regions SV radiallyextend from the first data region UA1 to the second data region UA2 inthe radial direction.

In the example shown in FIG. 6, the user data controller 62 arranges thetrack CCT in a circular shape in the first data region UA1. Further, theuser data controller 62 arranges the track SPT in a spiral shape in thesecond data region UA2. The user data controller 62 may arrange tracksin a spiral shape from the radial position IMP toward the radialposition IBP or arrange tracks in a spiral shape from the radialposition IBP toward the radial position IMP. It should be noted thattracks arranged in a spiral shape may be a single spiral or a multispiral.

FIG. 7 is a diagram showing an example of part of tracks arranged in aspiral shape in the second data region UA2. In FIG. 7, the inclinationθtd of the track direction with respect to the circumferential direction(hereinafter referred to as track angle) is shown.

In the example shown in FIG. 7, the user data controller 62 arrangestracks in the second data region UA2 at the track angle θtd with respectto the circumferential direction.

FIG. 8 is a diagram showing an example of tracks arranged in a spiralshape at the track angle θtd in the second data region UA2.

In the example shown in FIG. 8, the user data controller 62 arrangesfour tracks in a spiral shape in the second data region UA2 with a trackangle θtd of 3°.

FIG. 9 is a view showing an example of tracks arranged in a spiral shapeat the track angle θtd in the second data region UA2.

In the example shown in FIG. 9, the user data controller 62 arranges 20tracks in a spiral shape in the second data region UA2 with a trackangle θtd of 10°.

FIG. 10 is a diagram showing an example of the relation between theradial position in a case where a track is written in a spiral shape atthe track angle θtd in the second data region UA2 and the angle θdf ofthe head HD with respect to the track direction. In FIG. 10, thevertical axis represents the angle of the head HD with respect to thetrack direction (hereinafter referred to as difference angle) θdf, andthe horizontal axis represents the radial position. The difference angleθdf corresponds to the difference value (θs−θtd) between the skew angleθs and the track angle θtd. In FIG. 10, the line L31 shows a change inthe difference angle θdf with respect to the radial position(hereinafter referred to as a change in the difference angle θdf withrespect to the circular track) in a case where each track is arrangedconcentrically with the center of the disk DK. The change L31 in thedifference angle θdf with respect to the circular track corresponds tothe change L31 in the skew angle θs of the short actuator AC shown inFIG. 3. The line L101 shows a change in the difference angle θdf withrespect to the radial position (hereinafter referred to as a change inthe difference angle θdf with respect to the track with the track angleθtd) in a case where tracks are arranged in a spiral shape at the trackangle θtd in the second data region UA2.

In the example shown in FIG. 10, as indicated by the change L101 in thedifference angle θdf with respect to the track with the track angle θtd,the user data controller 62 arranges the track in a spiral shape at thetrack angle θtd of θtd 1, for example, 10° in the second data regionUA2. In this case, the difference angle θdf is a difference angle θdf 1smaller than the second boundary angle θba 2 at the radial position IBP.In other words, the head HD is inclined at the difference angle θdf 1smaller than the second boundary angle θba 2 with respect to the trackdirection at the radial position IBP. The difference angle θdf increasestoward the radial position IMP from the radial position IBP, and becomeslarger than the second boundary angle θba 2 at the radial position IP1.That is, a data pattern in which the magnetization pattern is disturbedby the head HD inward relative to the radial position IP1 can bewritten. Compared with the change L31 in the difference angle θdf withrespect to the circular track, in the change L101 in the differenceangle θdf with respect to the track with the track angle θtd, the regionin the radial direction in which the data pattern in which themagnetization pattern is disturbed by the head HD can be written isreduced. That is, compared with the case of reading tracks arranged in acircle in the second data region UA2, when tracks arranged in a spiralshape at the track angle θtd is read, the signal quality of the readdata, for example, SNR (Signal to noise ratio) can be improved.

FIG. 11 is a diagram showing an example of part of tracks arranged at atrack angle θtd that changes according to the skew angle θs in thesecond data region UA2.

In the example shown in FIG. 11, the user data controller 62, in thesecond data region UA2, arranges tracks at the track angle θtd whichchanges according to the skew angle θs by the write head WH based on thehigh frequency (HF) write signal, for example, at θtd=θba 3 (=θs).

FIG. 12 is a view showing an example of tracks arranged in a spiralshape at the track angle θtd changing according to the skew angle θs inthe second data region UA2.

In the example shown in FIG. 12, the user data controller 62, in thesecond data region UA2, arranges ten tracks in a spiral shape at thetrack angle θtd which changes according to the skew angle θs, forexample, at the track angle θtd which changes so that the differenceangle θdf becomes 0°.

FIG. 13 view showing an example of tracks arranged in a spiral shape atthe track angle θtd changing according to the skew angle θs in thesecond data region UA2.

In the example shown in FIG. 13, the user data controller 62, in thesecond data region UA2, arranges ten tracks in a spiral shape at thetrack angle θtd which changes according to the skew angle θs, forexample, at the track angle θtd which changes so that the differenceangle θdf becomes the second boundary angle θba 2.

FIG. 14 is a diagram showing an example of the track angle θtd changingaccording to the skew angle θs. In FIG. 14, the vertical axis indicatesthe track angle θtd and the horizontal axis indicates the radialposition in the second data region UA2. The line L141 shows an exampleof a change in the track angle θtd that changes so that the differenceangle θdf shown in FIG. 12 becomes 0°. The line L142 shows an example ofa change in the track angle θtd that changes so that the differenceangle θdf shown in FIG. 13 becomes a particular angle. Here, theparticular angle is, for example, an angle equal to or greater than thesecond boundary angle θba 2.

In the second data region UA2, when the skew angle θs is equal to orless than a particular angle, when the track angle θtd is changed sothat the difference angle θdf is the particular angle, the track goesoutward or has a circular shape. It does not have a spiral shape headinginward. Therefore in the second data region UA2, the user datacontroller 62 performs control so that the track angle θtd is greaterthan the lower limit value LLV. The lower limit value LLV is, forexample, an angle at which the track turns inward when the track angleθtd is changed so that the difference angle θdf becomes a particularangle in the second data region UA2.

FIG. 15 is a diagram showing an example of the relation between theradial position and the difference angle θdf with respect to the trackdirection in a case where the track is written in a spiral shape at thetrack angle θtd changing according to the skew angle in the second dataregion UA2. In FIG. 15, the vertical axis represents the differenceangle θdf, and the horizontal axis represents the radial position. FIG.15 shows the change L31 in the difference angle θdf with respect to thecircular track. The line L151 indicates a change in the difference angleθdf with respect to the radial position (hereinafter referred to aschange in as a first difference angle θdf) in a case where tracks arearranged in a spiral shape at a track angle θtd that changes so that thedifference angle θdf becomes 0° in the second data region UA2. The lineL152 indicates a change in the difference angle θdf with respect to theradial position (hereinafter referred to as change in as a seconddifference angle θdf) in a case where tracks are arranged in a spiralshape at a track angle θtd that changes so that the difference angle θdfbecomes the second boundary angle θba 2 in the second data region UA2.The line L133 indicates a change in the difference angle θdf withrespect to the radial position (hereinafter referred to as change in athird difference angle θdf) in a case where tracks are arranged in aspiral shape at a track angle θtd that changes so that the differenceangle θdf becomes θdf 2 in the second data region UA2. Here, 0<θdf 2<θba2.

In the example shown in FIG. 15, as indicated by the change L151 in thefirst difference angle θdf, the user data controller 62 arranges thetracks in a spiral shape at the track angle θtd [θtd(r)=θs(r), where ris the radial position] that changes such that the difference angle θdfbecomes 0° in the second data region UA2. In this case, the differenceangle θdf is 0° (θdf=0) in the second data region UA2, and is smallerthan the second boundary angle θba 2. As indicated by the change L152 inthe second difference angle θdf, the user data controller 62 arrangesthe tracks in a spiral shape at the track angle θtd [θtd(r)=θs(r)−θba 2,where r is tie radial position] that changes such that the differenceangle θdf becomes the second boundary angle θba 2 in the second dataregion UA2. In this case, the difference angle θdf is the secondboundary angle θba 2 (θdf=θba 2) in the second data region UA2. Asindicated by the change L153 in the third difference angle θdf, the userdata controller 62 arranges the tracks in a spiral shape at the trackangle θtd [θs(r)−θba 2<θtd(r)<θs(r), where r is the radial position]that changes such that the difference angle θdf becomes the θdf 2 in thesecond data region UA2. In this case, the difference angle θdf is θdf 2(0<θdf=θdf 2<θba 2) in the second data region UA2, and is smaller thanthe second boundary angle θba 2. Therefore, in order to ensure thesignal quality of the data at the time of reading, the user datacontroller 62 can adjust the length of tracks arranged in a spiral shapeat a track angle in the range of θs (r)−θba 2≤θtd(r)≤θs(r) in the seconddata region UA2.

The command processor 63 processes the command received from the host100. The command processor 63 includes a sector access processor 631,the command queue processor 632, a reordering processor 633, and a mediacache (MC) access processing unit 634. The sector access processor 631executes access processing to a particular sector according to thecommand. The command queue processor 632 queues commands. The reorderingprocessor 633 executes reordering processing for a plurality of commandsqueued in the command queue processor 632. The reordering processor 633performs, for example, reordering processing on a plurality of commandsso as to perform processing from a command having a short time to accessa designated sector. The MC access processor 634 executes accessprocessing to the media cache, for example, to the system area SA andthe second data region UA2 according to the command.

FIG. 16 is a diagram showing an example of an LBA according to the firstembodiment. In FIG. 16, the LBA (Logical Block Address) is divided intoa partition Part A and a partition Part B. The partition Part Acorresponds to the first data region UA1. The LBA corresponding to thepartition Part A includes, for example, 0000, 0001, 0002 to 0100 to0200. The partition Part B corresponds to the second data region UA2.The LBA corresponding to Part B includes, for example, 0201, 0202 0203to 300. In FIG. 16, the right hatched region indicates the LBAcorresponding to the second data region UA2.

Upon receipt of a command from the host 100, the command processor 63accepts the command from the host 100 when the command queue is vacant.The command processor 63 executes reordering processing for selecting acommand whose access time is short from the command queue.

The command processor 63 divides the LBA into a partition Part A and apartition Part B. When the command processor 63 receives a command foraccessing the partition Part A (hereinafter referred to as an A command)and a command for accessing the partition. Part B (hereinafter referredto as a B command) from the host 100, the command processor 63preferentially processes the A command. For example, when there is the Acommand at the time of reordering the command, the command processor 63preferentially processes the A command by adding a weight to the accesstime by the B command. As an example, the command processor 63 adds aweight to the access time by the B command according to the followingexpression.

Tro=Tac×Np   (Expression 1)

where Tro is a value for determining the priority in reordering. Thesmaller the Tro, the higher the priority. Tac is a predicted access timeto the sector corresponding to the LBA designated by the command. Npindicates the weight. When there is the A command at the time ofreordering the command, the command processor 63 adds a weight to the Bcommand according to the expression 1 so as to make it difficult for theprocessing of the B command to be selected.

FIG. 17 is a diagram showing an example of command processing accordingto the first embodiment. In FIG. 17, the command processor 63 includes acache CC1 that stores A command and B command. In FIG. 17, the plaincommand indicates the A command, and the right hatched command indicatesthe B command. It should be noted that the command processor 63 may havea cache for storing the A command and a cache for storing the B commandseparately. Further, for example, the host 100 may recognize the rangebetween the partition Part A and the partition Part B of the LBA. Inthis case, the host 100 indicates, for example, the A command or the Bcommand and inputs a command to the command processor 63.

In the example shown in FIG. 17, the command processor 63 stores the Acommand cmdD received from the host 100 in the cache CC1, and reordersthe A command cmd1A, A command cmd1B, B command cmd1C, and A commandcmd1D which have been stored. The command processor 63 determines thatthere is the A command in the plurality of commands stored in the cacheCC1 at the time of reordering, adds a weight to the B command cmd1B, andpreferentially processes the A command cmd1.

FIG. 18 is a flowchart showing an example of a method of determining thetrack angle θtd according to the first embodiment.

The system controller 130 calculates the track angle θtd(r) based on thedifference value between the skew angle θs(r) at the radial position rof the current head HD and the second boundary angle θba 2, for example,15° in the second data region UA2 (B1801). The system controller 130determines whether the track angle θtd(r) is smaller than the lowerlimit value LLV, or equal to or larger than the lower limit value LLV(B1802). When it is determined (“YES” an B1802) that the track angleθtd(r) is smaller than the lower limit value LLV, the system controller130 determines that the lower limit value LLV is the track angle θtd(r)(B1803) and ends the process. When it is determined. (“NO” in B1802)that the difference is equal to or larger than the lower limit valueLLV, the system controller 130 determines that the difference value,θs(r)−θba 2, calculated in B1801 is the track angle θtd(r), and ends theprocess.

According to the present embodiment, the magnetic disk device 1 includesthe actuator AC having an arm to which a head HD is attached at the tip,and the disk DK having the first data region UA1 and the second dataregion UA2. When the head HD is moved from the radial position OBP tothe radial position IBP in the first data region UA1 by the actuator AC,the skew angle θs of the head HD changes from the first boundary angleθba 1 to the second boundary angle θba 2. When the head HD is moved fromthe radial position IBP to the radial position IMP in the first dataregion UA1 by the actuator AC, the skew angle θs of the head HD changesfrom the second boundary angle θba 2 to the third boundary angle θba 3.The magnetic disk device 1 writes the high access data (hot data) in thefirst data region UA1 and writes the low access data (cold data and/orwarm data) in the second data region UA2. In addition, the magnetic diskdevice 1 writes data (track) in a spiral shape in the second data regionUA2. The magnetic disk device 1 can randomly perform access at highspeed in the first data region UA1 and can improve the reliability ofthe data written in the second data region. UA2. Therefore, it ispossible to provide the magnetic disk device 1 capable of efficientlywriting data on the disk DK.

Next, a magnetic disk device according to modified examples and anotherembodiment will be described. In the modifications and otherembodiments, the same reference numerals are attached to the same partsas those in the above embodiment, and a detailed description thereofwill he omitted.

(First Modification)

The magnetic disk device 1 of a first modification is different from theabove-described embodiment in the positioning control method of the headHD in the second data region UA2.

FIG. 19 is a block diagram showing an example of a positioning controlsystem SY1 of the magnetic disk device 1. FIG. 19 shows a control systemthat executes a feedback control system in tracking.

The magnetic disk device 1 has a plant control system (positioningcontrol system) SY1 for positioning the head HD. The positioning controlsystem SY1 includes a spiral track target position generation unit S1, astate estimation unit S2, a plant control unit S3, a plant S4, andcalculation units C1 and C2. In one example, the spiral track targetposition generation unit S1, the state estimation unit S2, the plantcontrol unit S3, and a calculation unit C1 are provided in the servocontroller 61. For example, the plant S4 corresponds to the head HD, theactuator AC, and the like. The positioning control system SY1 executesfeedback control.

The spiral track target position generation unit S1, in the second(dataregion UA2, generates a target position (hereinater referred to as aspiral position) Ptgt_spiral on the track in a spiral shape based on thecurrent position P on the disk DK (hereinafter referred to as the actualposition) of the plant S4. For example, the spiral track target positiongeneration unit S1 calculates the skew angle θs from the current radialposition of the head HD, calculates the track angle θtd based on thecalculated skew angle θs and the second boundary angle θba 2, andgenerates the next spiral position Ptgt_spiral based on the calculatedtrack angle θtd.

The state estimation unit S2 is a state observer, and has a model of theplant S4 (hereinafter referred to as a plant model) and an internalstate variable. The state estimating unit S1 estimates a target positionPsm on the disk DK (hereinafter referred to as an estimated position) ofthe plant S4 in the sample of the servo next to the current servo(hereinafter referred to as a next sample) of the plant S4 based on theplant model, the internal state variable, the driving amount U(hereinafter referred to as actual driving amount) of the plant S4, andthe actual position P of the plant S4.

The plant control unit S3, for example, controls the plant S4. The plantcontrol unit S3, for example, generates the actual driving amount U ofthe plant S4 based on the estimated position error Ep. The plant controlunit S3 may generate the actual driving amount U based on values otherthan the estimated position error Ep, for example.

The plant S4 is driven based on the actual driving amount U.

In the HDC 60, when a particular position (hereinafter referred to as adesignated position) on the disk DK from which data is read or on whichdata is written is designated, the calculation unit C1 receives thedesignated position Ptgt_dc and the next spiral position Ptgt_spiral byfeedback control. The calculation unit C1 outputs the target positionPtgt obtained by adding the spiral position Ptgt_spiral to thedesignated position Ptgt_dc to a calculation unit C2.

The state estimation unit 52 receives the actual position P and theactual driving amount U with respect to the position of the plant S4.The state estimation unit S2 outputs the estimated position Psm to thecalculation unit C2. The calculation unit C2 receives the targetposition Ptgt and the estimated position Psm. The calculation unit C2outputs the estimated position error Ep obtained by subtracting theestimated position Psm from the target position Ptgt to the plantcontrol unit S3.

The plant control unit S3 receives the estimated position error Ep. Theplant control unit S3 outputs the actual driving amount U to the plantS4. The plant S4 is driven according to the actual driving amount U andmoves to the actual position P. It should be noted that the actualdriving amount U corresponds to the current value for driving the VCM14, for example.

FIG. 20 is a flowchart showing an example of the positioning controlmethod of the head HD in the second data region UA2 according to thefirst modification.

The system controller 130 calculates the skew angle θat the currentradial position of the head HD (B2001). The system controller 130calculates the track angle θtd based on the skew θs (B2002). Forexample, the system controller 130 calculates (determines) the trackangle based or the method shown in the flowchart of FIG. 18. The systemcontroller 130 calculates the radial position (target position) Ptgt ofthe next head HD (B2003) and ends the process.

According to the first modification, the magnetic disk device 1 canposition the head HD at a target position on the tracks in a spiralshape in the second data region UA2. Therefore, the magnetic disk device1 can improve the accuracy of servo control.

(Second Modification)

In the magnetic disk device 1 of a second modification, theconfiguration of the disk DK is different from those of theabove-described embodiment and modification.

FIG. 21 is a cross-sectional view schematically showing an example of aconfiguration of a disk DK according to the second modification. FIG. 21schematically shows a cross section taken along line XXI-XXI shown inFIG. 2.

In the example shown in FIG. 21, the disk DK includes a non-magneticsubstrate SUB, a soft magnetic layer SUL (Soft Under Layer) as aunderlayer, a recording layer RCL, a protective layer PTL, and alubricating layer LBL all of which are laminated in this order. That is,the soft magnetic layer SUL is laminated on the surface of the substrateSUB, the recording layer RCL is laminated on the surface of the softmagnetic layer SUL, the protective layer PTL is laminated on the surfaceof the recording layer RCL, and the lubricating layer LBL is laminatedon the surface of the protective layer PTL. The recording layer RCLholds data by controlling the magnetization in the vertical direction bythe recording magnetic field applied from the recording magnetic poleconstituting the write head WH. For the thickness TH of the recordinglayer RCL, the, second data region UA2 is thicker than the first dataregion UA1. Further, the thickness of the protective, layer PTL is thesame in the first data region UA1 and the second data region UA2, andaccording to the change in the thickness TH of the recording layer RCL,the second data region UA2 rises higher than the first data region UA1.The thickness of the lubricating layer LBL is also the same in the firstdata region UA1 and the second data region UA2 and rises at the seconddata region UA2 higher than at the first data region UA1 according tothe change in the thickness TH of the recording layer RCL.

In the second data region UA2, the low access data (cold data and/orwarm data) is written. Because of this, the data written in the seconddata region UA2 should be stored for a long time. Thus, the second dataregion UA2 is designed to have a high thermal stability, compared withthe first data region UA1, so that it is possible to store data for along time in the second data region UA2. The thermal stability ofrecording media such as a disk DK is represented by KuV/kbT. Here, Ku isthe magnetic anisotropy energy of the magnetic particles of therecording layer RCL, V is the volume of the magnetic particles of therecording layer RCL, kb is the Boltzmann constant, and T is thetemperature. According to this equation, in order to improve the thermalstability, for example, the volume V of magnetic particles (=the filmthickness of the recording layer RCL multiplied by the area of themagnetic particles of the recording layer RCL) is increased. As comparedto the case where the thickness TH of the recording layer RCL of thesecond data region UA2 is substantially equal to the thickness of therecording layer RCL of the first data region UA1, the thermal stabilityof the second data region UA2 can be improved in the case where thethickness TH of the recording layer RCL of the second data region UA2 isgreater than the thickness of the recording layer RCL of the first dataregion UA1. Therefore, in the second modification, the recording layerRCL has a larger thickness TH in the second data region UA2 than in thefirst data region UA1.

FIG. 22 is a diagram showing an example of a change in the thickness THof the disk DK according to the second modification. In FIG. 22, theline L221 shows the change in the thickness TH of the disk DK from thefirst data region UA1 to the second data region UA2 according to thesecond modification. A line L222 indicates the thickness TH (=TS0) ofthe disk DK when the disk DK does not change from the first data regionUA1 to the second data region UA2.

In the example shown in FIG. 22, the thickness of the disk DK accordingto the second modification gradually increases from the thickness TH0 ofthe radial position OP1 of the first data region UA1 toward thethickness TH1 of the radial position IMP of the second data region UA2

According to the second modification, in the magnetic disk device 1includes the disk DK where the thickness TH of the recording layer inthe second data region UA2 for writing the low access data (cold dataand/or warm data) is thicker than the thickness TH of the recordinglayer of the first data region UA1 in which the high access data (hotdata) is written. Therefore, the magnetic disk device 1 can stably storedata in the second data region UA2 over a long period of time.

Second Embodiment

A magnetic disk device 1 of a second embodiment is different from theabove-described embodiment and modification in that the interface (IF)for receiving the A command and the B command are separately provided.

FIG. 23 is a schematic diagram showing an example of the configurationof the magnetic disk device 1 according to the second embodiment.

An HDC 60 further includes a command processor 64. The command processor64 has the same configuration as a command processor 63. That is, thecommand processor 64 includes a sector access processor, a command queueprocessor, a reordering processor, and an MC access processor.

FIG. 24 is a diagram showing an example of an LBA according to thesecond embodiment. In FIG. 24, the LBA is separately and independentlyallocated to the drive A and the drive B. The drive A corresponds to thefirst data region UA1, and corresponds to the command processor 63, forexample. The drive B corresponds to the second data region UA2, forexample, corresponds to the command processor 64. The LISA correspondingto the drive A includes 0000, 0001, 0002 to 0100 to 0200. The LBAcorresponding to the drive B includes 0000, 0001, 0002 to 0100. In FIG.24, the right hatched region indicates the LBA corresponding to thesecond data region UA2.

In an example shown in FIG. 24, in the system controller 130 (HDC 60),the A command is input to the drive A by the host 100, and the B commandis input to the drive P by the host. 100. The system controller 130preferentially processes the A command. The system controller 130determines whether the A command is stored in the drive A. When it isdetermined that the A command is stored in the drive A, the systemcontroller 130 processes the A command and does not process the Bcommand stored in the drive B. When it is determined that the A commandis not stored in the drive A, the system controller 130 processes the Bcommand stored in the drive B.

FIGS. 25 and 26 are diagrams showing an example of command processingaccording to the second embodiment. In FIGS. 25 and 26, the commandprocessor 63 includes the cache CC1 that stores the A command and aninterface IF1 that is connected to the host 100. The command processor64 includes a cache CC2 for storing the B command and an interface IF2connected to the host 100. In FIGS. 25 and 26, the plain commandindicates the A command, and the right hatched command indicates the Bcommand. In the example shown in FIG. 25 and FIG. 26, for the systemcontroller 130, the command processor 63 receives the A command from thehost 100 via the interface IF1, and to the command processor 64 receivesthe B command from the host 100 via the interface IF2.

In the example shown in FIG. 25, the system controller 130 (HDC 60)determines that the A command is stored in the cache CC1 of the commandprocessor 63 corresponding to the drive A, and reorders a plurality of Acommands stored in the cache CC1 and processes the A command cmd1B. Atthis time, the system controller 130 does not process the B commandstored in the cache CC2 of the command processor 64 corresponding to thedrive B.

In the example shown in FIG. 26, the system controller 130 (HDC 60)determines that the A command is not stored in the cache CC1 of thecommand processor 63 corresponding to the drive A, and reorders aplurality of B commands stored in the cache CC2 and processes the Bcommand cmd2B.

FIG. 27 is a flowchart showing an example of command processingaccording to the second embodiment.

The system controller 130 determines whether the A command is stored inthe cache CC1 of the A drive (B2701). When it is determined that the Acommand stored (“YES” in B2701), the system controller 130 processes theA command (B2702) and ends the process. When it is determined (“NO” inB2702) that the A command is not stored, the system controller 130determines whether the B command is stored in the cache CC2 of the Bdrive (B2703). When it is determined (“YES” in B2703) that the B commandis stored, the system controller 130 processes the B command (B2704) andends the process. When it is determined (“NO” in B2703) that the Bcommand is not stored, the system controller 130 ends the process.

According to the second embodiment, the magnetic disk device 1 includesan interface (IF) for receiving the A command and an interface (IF) forthe B command separately. Therefore, the magnetic disk device 1 canefficiently access the first data region UA1 and the second data regionUA2.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetic disk device comprising: a diskincluding a first region and a second region different from the firstregion; a head that writes data on the disk and reads data from thedisk; an actuator that positions the head on the disk; and a controllerwhich positions the head by driving the actuator and writes data, in thefirst region and the second region with the head, a skew angle of thehead with respect to a circumferential direction of the disk varyingwithin a first angle in the first region, and varying, in the secondregion, from a second angle larger than the first angle to a third anglelarger than the first angle and the second angle.
 2. The magnetic diskdevice according to claim 1, wherein the controller writes first data inthe first region and writes in the second region second data with alower access frequency than the first data.
 3. The magnetic disk deviceaccording to claim 2, wherein the first data includes first user data,and the second data includes at least one of media cache data, systeminformation, and second user data with a lower access frequency than thefirst user data.
 4. The magnetic disk device according to claim 1,wherein the controller writes data in the second region so that at leastone of a linear recording density and a track density is lower in thesecond region than in the first region.
 5. The magnetic disk deviceaccording to claim 1, wherein the controller writes data in a spiralshape in the second region.
 6. The magnetic disk device according toclaim 5, wherein the controller writes data at a fourth angle withrespect to the circumferential direction in the second region.
 7. Themagnetic disk device according to claim 5, wherein the controller writesdata according to the skew angle in the second region.
 8. The magneticdisk device according to claim 7, wherein the controller writes thefirst data so that a difference value between the skew angle and afourth angle of the first data with respect to the circumferentialdirection is zero in the second region.
 9. The magnetic disk deviceaccording to claim 7, wherein the controller writes the first data sothat a difference value between the skew angle and the fourth angle ofthe first data with respect to the circumferential direction is smallerthan the second angle in the second region.
 10. The magnetic disk deviceaccording to claim 7, wherein the controller writes the first data sothat a difference value between the skew angle and the fourth angle ofthe first data with respect to the circumferential direction is equal tothe second angle in the second region.
 11. The magnetic disk deviceaccording to claim 1, wherein the third angle θtd(r) is an angle in arange of θs(r)−θth≤θtd(r)≤θs(r) at a radial position r of the disk,θs(r) is an skew angle at the radial position r, θth is an angle thatensures a quality of write/read processing, and when a difference angleθdf between the skew angle θs(r) at the radial position r and the thirdangle θtd(r) is an angle in a range of 0≤|θdf(r)|≤θth, the controllerwrites data at the third angle θtd(r) with respect to thecircumferential direction at the radial position r.
 12. A magnetic diskdevice comprising: a disk including a first region and a second regiondifferent from the first region; a head that writes data on the disk andreads data from the disk; and a controller which positions the head bydriving the actuator and writes data in the first region and the secondregion with the head, a thickness of the second region being greaterthan that of the first region.
 13. The magnetic disk device according toclaim 12, wherein the first region has a first recording layer in whichdata is written by a magnetic field applied from the head, the secondregion has a second recording layer in which data is written by amagnetic field applied from the head, and a thickness of the secondrecording layer is larger than a thickness of the first recording layer.14. A magnetic disk device comprising: a disk including a first regionand a second region different from the first region; a head that writesdata on the disk and reads data from the disk; and a controller whichpreferentially processes a first command for executing a read/writeprocessing on a first region of the disk over a second command forexecuting a read/write processing on a second region of the disk. 15.The magnetic disk device according to claim 14, wherein the secondregion is located on an inner peripheral side relative to the firstregion.
 16. The magnetic disk device according to claim 14, wherein whenthe controller holds the first command and the second command, thecontroller performs reordering so as to preferentially process the firstcommand over the second command apparatus.
 17. The magnetic disk deviceaccording to claim 14, wherein the controller includes a firstprocessing unit that stores the first command and processes the firstcommand and a second processing unit that stores the second command andprocesses the second command.
 18. The magnetic disk device according toclaim 17, wherein the first processing unit and the second processingunit are physically separated.
 19. The magnetic disk device according toclaim 17, wherein the controller processes the first command when thefirst command is stored in the first processing unit.
 20. The magneticdisk device according to claim 17, wherein the controller processes thesecond command when the first command is not stored in the firstprocessing unit.